What color were the dinosaurs? It's a question that people have puzzled over for close to 200 years, and one that many long believed to be unanswerable. But a few years ago, scientists discovered that microscopic structures called melanosomes could be used to reveal prehistoric creatures' true hues.

Now, an international team of researchers studying the melanosomes of a four-winged dinosaur named Microraptor has made a remarkable discovery: Microraptor was completely black, but its feathers shone with a glossy hint of blue. In other words, it's plumage was iridescent — and that, say the researchers, provides us with some surprising insights into the early evolution of feathers.

"One of the things modern birds are known for is their elaborate visual displays," explains Mark Norell, chair of The American Museum of Natural History's Paleontology Division and coauthor on the study. These displays, which have no bearing on a bird's capacity for flight, can serve any number of functions — to attract a mate, for instance, or to ward off potential predators.

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Paleontologists have long hypothesized that visual displays played an equally important role in feathered dinosaurs. Until recently, however, there's been no way for them to prove it. That's where melanosomes come in.

Melanosomes are pigment-packing structures that can be found in the feathers of dinosaurs and modern birds alike. They're very small (you can fit around 100 of them across the width of a human hair), but specific melanosome shapes correspond to unique colors. Spherical melanosomes, for example, look rust-colored, while longer, rod-shaped ones appear black. Stack enough melanosomes together into specially organized layers and you get unique spectral properties, like iridescence.

By comparing Microraptor's melanosomes to those found in the feathers of 168 modern-day birds, Norell and his colleagues were able to gain unprecedented insight into what this animal looked like when it was alive around 130 million years ago.

"Iridescence is something that has shown up multiple times in the evolution of modern birds and their common relatives, and it's often used in displays," explained Norell. The fact that Microraptor was largely iridescent, he says, suggests that feathers may have initially evolved for purposes other than flight. [Science]Top image by Jason Brougham, second reconstruction by Mick Ellison, via AAAS/Science

Want to know more about Microraptor's iridescent feathers? Here's your chance to ask the researchers yourself:
The American Museum of Natural History has teamed up with io9 to host a live webcast discussion
tomorrow, March 9th, starting at 12:30 pm EST.

I'll be meeting with AMNH Paleontologist Mark Norell and Museum senior principal artist Mick Ellison to talk about their research; but we'll also be fielding questions submitted to comments@amnh.org, or via Twitter with the hashtag #dinofeathers. Feel free to submit questions in advance!

Remember: the webcast starts tomorrow at 12:30 PM Eastern time. You'll be able to watch the webcast live on AMNH, or on io9 via live feed. Hope to see you there!